ANN ALES • Ser. hist, nat. • 9 • 1999 • 1 (15) 
original scientific paper UDC 595.3:591.16(262-11) 
OCCURRENC E O E LARVAE O F SCYLLARUS ARCTUS (CRUSTACEA , 
DECAPODA , SCYLLARIDAE ) IN TH E EASTERN MEDITERRANEAN ­PRELIMINARY RESULTS 

Ulrich FIEDLER 

Abt. Meereszoologie, Institut für Meereskunde, Düsternbrooker Weg 20, D-24105 Kiel, Germany 
Ehud SPANIER 

The Leon Recartatt Center for Maritime Studies and Department for Maritime civiüzations, University of Haifa, Mount Carmel, 
Haif a 31905, Israel 
ABSTRACT 

Phyllosoma larvae of the broad lobster Scyilarus arctus (Crustacea: Decapoda: Scyllaridae) were sampled by plankton nets in the Eastern Mediterranean. A scheme for distinguishing between larval stages is suggested. It describes the characteristic features of phyllosoma stages 3 to 12. Phyllosomes of the studied species were found almost all year round and nearly all stages were represented in the samples. Findings of early stage larvae may indicate a spawning season mainly from February to April and from July to September. Most larvae were caught at considerable distances offshore. Larvae were sampled mostly in four long-term persistent or recurrent eddies. Data from physical studies; imply an increased probability that phyllosomes can be trapped in eddies for a relatively long period of time while drifting away from the coast. The possible ecological significance of this finding is discussed. 
Key words: Zooplankton, Phyllosoma larvae, Crustacea, Decapoda, Scyllaridae, Scyilarus 
INTRODUCTION 

In comparison with the wealth of information avail­able on the biology and ecology of larval stages of clawed lobsters, Nephropidae (e.g., Cobb and Wahle, 1994; Factor, 1995) and of spiny lobsters, Palinuridae (e.g., Kittaka, 1994), the knowledge of the larval stages of slipper lobsters, Scyllaridae, is scanty, especially on the Mediterranean species. In the Eastern Mediterranean this family is represented by two genera, Scyllarides and Scyilarus (Holthuis, 1991). Only one species of the first genus, S. latus, (Latreille, 1803), and two of the latter, 5. arctus (Linné, 1758) and S. pygmaeus {Bate, 1888), are reported from this area (Seridji, 1989). The complete larval development of none of these species is known. Within the genus Scyilarus, phyllosoma larvae spend up to four months drifting in the ocean (Philfips & Mc William, 1989). How is larval dispersal controlled in the open sea in view of various physical "obstacles" such as eddies, or do they use these circling currents as a "development-loop" until metamorphosis? 
In the Eastern Mediterranean, mesoscale eddies are recognized as potentially important oceanographic fea­tures (Robinson et ai, 1987, 1991). In this area, four long-term persistent or recurrent eddies have been in­vestigated: a cyclonic, cold-core eddy south of Crete, two anti-cyclonic eddies at the Herodotus basin (Mersa Matruh and one eddy just north of it) and the anti-cy­clonic Shikmona eddy south of Cyprus (Brenner, 1993). The diameter of the last eddy is approximately 150 km. Krom el al. (1991) found the waters in the core of the Shikmona eddy near Cyprus to be sealed off the sur­rounding waters. This is apparently true also for the Mersa Matruh and the eddy off Crete (Hecht, personal communications). 
Stephensen (1923) found numerous phyllosoma lar­vae of the broad lobster S. arctus in plankton samples of the Thor expedition (1908-1910) in the Mediterranean. 
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ANN ALES • Ser. hist, nat. • 9 • 1999 • 1 (15) 
Ulrich fiiOlfM & Ehwd SPANIER: OCCURRENCE O F LARVAE O F SCYUAKUS ARCTUS (CRU5TACEA, DECAPODA, SCYLLARIDAE) .... 153-1 53 
He was able to distinguish the different larval stages starting with phyllosoma stage I that had been previ­ously described by Dohrn (1870) based on larvae hatched from eggs of 5. arctus in the laboratory. 
The identification of larvae for the present study was based on Stephensen (1923). Our findings suggest sev­eral additions and corrections of his staging system, which are briefly stated in the identification scheme below. 
Larvae of only two species of Scyllarus have been successfully reared in the laboratory (Robertson, 1968: Scyllarus americanus; Ito & Lucas, 1990: Scyllarus demani). Their descriptions of larval stages were used to confirm our staging system. As long as there are not enough results from laboratory rearing experiments, a key based on defining stages from field material may be a useful tool, despite its limitations. Thus, identification of larvae enables the attempt done in the present study relating their spatial and temporal distribution to their physical environment. 

MATERIALS AN D METHODS 

The larvae used in this sUidy were collected during cruises conducted by the Israel Océanographie and 
25°Limnological Research (IOLR), Haifa, as part of the in­ternational POEM (Physical Oceanography of the East­ern Mediterranean) Program and the lOLR-Eddy-Pro­gram. From the summer of 1988 until the spring of 1990 several cruises were made with the R/V Shikmona II in the Eastern Mediterranean. A total of (50) stations, lo­cated in two arrays, were sampled in the Eastern Medi­terranean. The locations of the sampling stations are given in Figure 1. 

During these cruises, oblique plankton hauls were taken using a General Oceanics plankton net (60 cm in diameter, 500 pm mesh size) and a mesopelagic net (1 m2 squared mouth, 1000 pm mesh size), both equipped with a 25 kg depressor and a General Oceanics digital flow meter. A neuston net (50 x 20 cm half submerged mouth, 500 pm mesh size) was also used. During the POEM-cruises 1988 - summer 1989 only the General Oceanics net was employed and from fall 1989 - spring 1990 only the mesopelagic net was used. The General Oceanics net and the neuston net were used alternating during the lOLR-eddy-program cruises. Samples were taken randomly at all times. Approximately 400 m J of seawater were filtered per haul (General Oceanics and mesopelagic net). The neuston net was towed for 15 minutes with a speed 2 kn, resulting 0.5 nm towing range. 
 30° 35 ° 
25° 30 ° E 35° 

Fig. 1: Sampling stations of the present study. Dots: POEM cruises, triangles: IOLR eddy cruises. 
SI. 1: Vzorčevalne postaje. Pike: križarjenja v organizaciji POEM (Physical Oceanography of the Eastern Mediter­ranean). Trikotniki: križarjenja v organizaciji IOLR (Israel Oceanography and Limnological Research) za 
preučevanje morskih vrtincev. 

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Ulrich FIEDLER & Ehud SPANIER: OCCURRENCE O f l.ARVAE O F SCYLLARUS ASCTUS (CRUSTACEA. OECAPODA, SCYLLARIDAE).... 153-55 8 
Tab. 1: Identification scheme for phyllosoma stages of Scyllarus arctus. 
Tab. 1: Identifikacijska shema stadijev ülosom raka Scyllarus arctus. 
List of abbreviations: Abd-Abdomen; biram biramous; Cs-Cephalic shield; L-lengtb; Mx-Maxffla; Mxp-Maxilliped; 
Per-Pereiopod (Per 1-4: numbers of natatory setae on the exopodite); Pleop-Pleopod; pres.-present; T-total; Th-
Thorax; Urop-Vropods; W-width. 
Dimensions are given in mm. 

Stage 3 4 5 6 7 8 9 10 11 12 
Stephensens system Ml IV V V VI VI VII VIII IX 
No exam. 2 4 1 3 5 3 3 1 2 
T-L 3.3-3.4 4.3-4.9 6.1 7,0-7.9 10.1-12.3 12.8-13.7 15.5-17 19 21.6-24.4 
Cs-L 2.2-2.3 2.9-3.2 4.3 4.9-5.5 7.0-8.3 8.7-9.2 10.2-11.9 12.1 12.7-14.5 
Cs-W 2.3-2.5 3.2-3.6 4.7 5.6-6.3 8.5-10.4 10.7-11.2 12.3-13.9 15.0 16.1-18.0 
Th-W 1.2 1.5-1.8 2.2 2.5-2.7 3.3-4.1 4.5-4.8 5.2-5.8 6.2 6.8-7.6 
Cs-W/Th-W 2.0-2.1 2-1-2.2 2.1 2.2-2.3 2.3-2.6 2.3-2.5 2.3-2.5 2.4 2.4 
Abd-L 0.3 0.4 0.5 0.6-0.7 1.0-1.5 1.5-1.9 2.0-2.6 3.25 5.0-5.7 
Abd-W 0.2-0.3 0.3-0.4 0.6 0,7-0,9 1.3-1.9 2.0-3.0 2.9-3.2 3.8 S.0-5.6 
Mxpl o o <Mx2 <Mx2 =Mx2 =Mx2 =Mx2 =Mx2 biram 
Perl 10 12-13 14 15-16 19-22 21-22 23 24 25-27 
Per2 10 12-13 14 15-16 20-22 22-23 23 24 25-27 
Per3 6-7 8-11 11 13 17-19 19-22 21 22 24-25 
Per4 2 4-7 ? 9-11 15-16 17 19 20 21-23 
Per5-L 0.03 0.03-0.2 0.3 0.2-0.3 0.4-0.7 0.6 1.2-1.4 1.8 3.5-4.1 
Gills o 0 0 0 0 o 0 o pres. 
Pleop 0 0 pres. pres. bilobed bilobed bilobed, 
elongated Urop 0 o 0 bilobed bilobed bilobed bilobed bilobed Abd, concav concav concav slightly straight straight slightly convex 
concav convex 
Samples were preserved in 4% buffered formalde­hyde/seawater. Specimens were examined and meas­ured in natural seawater. The identification of specimens followed Stephensen (1923). In addition his staging sys­tem was modified. A brief identification table for the phyllosoma stages of S. arctus was developed (Table 1). This scheme uses morphological and morphometrica! features; yet, mainly morphological characters were used for the final definition of stages. The most charac­teristic features are emphasized in the text of Table 1 by bold letters. Due to the relatively small number of specimens, no means or medians are given. This scheme is based only on material of the present study. Some phyllosoma stages are, therefore, not included. 
RESULTS AN D DISCUSSION 

A total of 32 phyliosoma-iarvae were found in these samples, 24 of which were identified as S. arctus larvae. Two of the remaining phyllosoma are most probably Scyllarides latus larvae (stage II), since they resemble closely the known first stage larvae of this species. Six phyllosoma could not be identified until now. A brief scheme for the identification of phyllosoma stages of S. arctus is presented in Table 1. 
Sizes and morphological features of sampled phyllo­soma agree well with Stephensen's (1923) description. We added to his larval description some morphological and morphometrica! data. A detailed identification key to the phyllosoma stages of S. arctus is in preparation. The main difference between our scheme and Stephensen's is the splitting of his stages V and VI into at least two additional stages respectively. The absence or presence of uropods and the dimensions of cephalic shield and thorax shield are the key features for separat­ing our stages 5 and 6. The gap between our stage 6 and 8 let us hypothesize a 7th phyllosoma stage, despite no specimens being sampled. The drastic increase in the number of setae per pereiopod between our stages 6 and 8 and the morphometrical data suggest a presence of an intermediate stage. The 8th and 9 i h stages are mainly distinguished by morphometrical differences. 
Two Scyllarus species have been reared in the labo­ratory (Robertson, 1968; I to & Lucas, 1990). Both de­veloped within a few weeks and passed through 7 to 8 phyllosoma stages. There are only slight differences in the total length and development of maxilliped 1 and natatory setae on pereiopods between S. arctus and S. americanus stages 3-8 (Robertson, 1968). Uropods, pleopods and gills appear earlier in 5. americanus lar­
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ANN ALES • Ser. hist, nat. • 9 • 1999 • 1 (15) 
Ulricti FIEDLER t< Ehud 5FANIER: OCCURRENCE O f LARVAE OF SCYUMUS AtfCTLfS (CRUSTACEA, DECARODA. SCYUARIDAE) .... 153-S5S 
vae. 5. demani (I to & Lucas, 1990) differs in size from 5. arctus, but the development of morphological features is similar. 5. americanas and 5. arctus develop natatory setae on pereiopod 4 in stage 4, while S. demani devel­ops such setae in stage 5. Last larval stages of 5. ameri­canus and S. demani are smaller than 5. arctus stage 12. 
S. kitanoviriosus stage 8 (Wada et a!,, 1989) and 5. timidus stage 9 (Ritz, 1977) fall into approximately the same size range we found in 5. arctus, in agreement to Stephensen's findings. Stephensen's system already consisted of 9 stages, more than described by Robertson and Wada et a!. (1989). The duration of larval develop­ment of 5. americanas described by Robertson is by far shorter than the duration of larval life suggested by lar­val findings for other species. Therefore the number of instars may vary, whereas the general developmental features remain constant. 
Phyllosoma larvae of 5. arctus were found in ail sea­sons except winter (Tab. 2). Nearly all phyllosoma stages are represented in the samples. Larval stages in March ranged from stage 4 up to the last larval stage. Younger stages were found in spring, and fall; latest stages in spring and summer. Most larvae were found in March (54.2%) and May (20.8%). Rothlisberg et a!. 
37c 
35° 
33 ° 
31c [ ;-;.;•-• j v^ - .;.,;.;.;•••• _ _ 
25 °

(1994) found significant differences in larval catches of stage I larvae between 142 pm and 500 pm mesh size. Since we did not use any net with less than 500 pm mesh size, the lack of stage I and II larval catches may be explained. 
Basing on plankton material from the Mediterranean Sea, Stephensen (1923) suggested that the main spawn­ing season was in summer. Zariquiey Alvarez (1968) found ovigerous females in the Western Mediterranean from February to April and from July to September. Our sampling of phyitosomes within the early stages con­firms the results of Zariquiey Alvarez, with the exception of one stage 3 phyllosoma found in November. It may 
Tab. 2: Times and stages of sampled phyllosoma larvae. Tab. 2: Meseci in stadiji vzorčenih filosom. 
Month / Stages  3  1 4  5  6  7  8  9  10  11  12  
March  3  1  1  2  2  2  1  1  
May  1  3  1  
August  1  
September  1  1  1  
November  1  !  1  

35 ° 

 30° E 35° 
Fig. 2: Sampling locations of phyllosoma larvae of Scyliarus arctus of the present study and schematic general 
circulation of the Eastern Mediterranean (from Robinson et al., 1991). Roman numbers: phyllosomes's stage; 
names of gyres according to Robinson et ai. (1991). 
SI. 2: Vzorčevalne lokacije filosom raka Scyliarus arctus in shematsko splošno kroženje vzhodnega Sredozemskega 
morja (po Robinsonu et ai., 1991). Rimske številke: stadiji filosom; imena spiral po Robinsonu et ai. (1991). 

156 


ANNALES - Ser. hist. nat. • 9 • 1999 - 2 (17) 
Ulrich FIEDLER & Ehud SPANIER- OCCURRENC E O f L Ali VAE OF SCYLLARUS AKCTUS {CRVSTACtA, DECAPODA . SCVLLARiDA ß ..., 1S3-TSS 
indicate a different spawning pattern in the Eastern Mediterranean. Similarly, Spanier et al. (1988) found that the spawning season of Scyllarides latus in the southeastern Mediterranean is different, to a certain ex­tent, from the spawning season observed for the same species by Martins (1985) in the Azores, because of faster increase of water temperature in the spring in the southeastern Mediterranean. 
Adults of S. arctus are known from all parts of the Mediterranean Sea (Holthuis, 1991; Hoithuis & Gottlieb, 1958; Stephensen, 1923). They live in relatively shallow waters preferring muddy bottom (Pippitone, personal communications). While adults are reported from Israeli and Egyptian coasts (Holthuis & Gottlieb, 1958), no phyllosoma were found close to these coasts (Fig. 2). Most larvae were caught far away with two found as far as about 260 km off the coast. 
Larvae (Fig. 2) were sampled mostly in the eddy south of Crete (cold-core eddy), Mersa Matruh and its northern neighbor gyre (south-east of Crete) and Shik­mona eddy (south of Cyprus). Only two phyllosoma were found away from any eddy structure south of Crete. However, since most cruises were aimed for measurements of physical and chemical characteristics of eddies, the sampling pattern of larvae may be imbal­anced. it is therefore suggested to extend the sampling range of the present preliminary study also to areas away from eddies. 
Drifter experiments south of Crete showed that buoys that had been trapped for days or weeks in eddies moved for unknown reasons to the eddy boundaries, left the eddies, but became trapped once more, by neigh­boring eddies (A. Hecht, personal communications). The ^ planktonic life of phyllosomes lasts several months. This implies an increased probability that they will be trapped in eddies while they drift away from the coast. Obviously there is a "trade off' between the advantage of reaching uninhabited coasts and the risk of being lost at sea. The amount of time larvae actually spend in a certain eddy has not been calculated and it is not known where they emerge. Yet, this explains the high dispersal of larvae. Long planktonic larval-life and high dispersal often correlate with a broad niche breadth in the adults. High larval dispersal reduces intraspecific competition that is of particular importance in environments with highly limited resources. The data of the present preliminary study is based on a relatively small number of phyllosomes. There is a clear need to expand the sample size, spatial and temporal scope of the coverage in future studies to verify the trends suggested here. 

ACKNOWLEDGMENTS 

The authors wish to thank M.D. Krom and A. Hecht for supporting lab facilities and ship time during POEM and lOLR-Eddy cruises and Cpt. A. Ben Nun, the crew of R/V Shikmona II and S. Kourilov and J. Bishop for as­sistance and cooperation. 
Fig. 3: Phyllosoma larva of the broad lobster Scyllarus arctus (Photo: E. Spanier). Sl. 3: Larva fdosoma raka vrste Scyllarus arctus (Foto: E. Spanier). 
POJAVLJANJ E LAR V RAK A SCYLLARUS ARCTUS (CRUSTACEA , DECAPODA , 
SCYLLARIDAE ) V VZHODNE M SREDOZEMLJ U - PREDHODN I REZULTAT I 

Ulrich FIEDLER 

Abt. Meereszoologie, Institut für Meereskunde Düste rn brooker Weg 20, D-24105 Kiel, Germany 
Ehud SPANIER 

The Leon Recanaii Center for Maritime Studies in Department for Maritime Civilizations, University of Haifa, Mount Cannel, 
Haifa 31905, Israel 

POVZETEK 

Avtorja sta s planktonsko mrežo lovila in vzorčevala filosome raka nagajivca Scyllarus arcfus (Crustacea: Decapoda: Scyllaridae) v vzhodnem Sredozemlju. Na osnovi vzorčenja sta pripravila shemo za ločevanje med 
W&frH 

ANN ALES • Ser. hist, nat. • 9 • 199 9 • 1 (15) 
Ulrich FiEDLER & Ehucf SPANrER: OCCURRENCE Of IARVAEOE 5CVi.iAi?L/5 AfiCTUS (CRUSTACEA, DECAfOOA, SCVLLAmOAi) ... . 153-158 
razvojnimi stadiji larv, z opisi značilnosti stadijev filosom od 3-12. Filosome preučevane vrste so hiie najdene med skoraj vsakim vzorčenjem v teku leta in v vzorcih so bili zastopani skoraj vsi stadiji. Dobljeni zgodnji razvojni stadiji larv kažejo na to, da drstitveno obdobje poteka predvsem med februarjem in aprilom ter med julijem in septembrom. Večina larv je bila ujeta daleč od obrežja. Larve so bile vzorčene v štirih območjih s stalnimi aH ponavljajočimi se cirkulirajočimi vrtinci. Podatki teh raziskav kažejo na verjetnost, da se filosome lahko ujamejo v vrtince za razmeroma dolgo obdobje, ko jih nosi proč od obrežja. Avtorja razglabljata o možnem ekološkem pomenu teh odkritij. 
Ključne besede: zoopiankton, filosome, raki, deseteronožci, medvedji raki, Scyllarus arctus, razširjenost, vzhodno Sredozemlje 
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